1. Field of the Invention
The present invention relates to latch assemblies for installation at more than one backset distance.
2. Description of the Related Art
The backset measurement of a door latch assembly is the distance between the forward extremity of the stationary casing longitudinally rearwardly to the transverse axis about which the latch operator moves for extending and retracting the bolt of the latch construction. The two standard backset dimensions for doors are 23/8 inches and 23/4 inches. Various of the manufacturers have produced single models of latch constructions which allow adjustment of the backset mesurement.
U.S. Pat. No. 4,664,433 to Solovieff issued on May 12, 1987 discloses a latch assembly with a backset adjustment. However, as pointed out by Wheatland et al. in U.S. Pat. No. 5,562,314 issued on Oct. 8, 1996, the bolt part may fall behind the casing part after simultaneous helical movement has begun which in turn can result in the bolt part falling out of the face plate and jamming. Similar problem exists in U.S. Pat. No. 4,372,594 to Gater issued on Feb. 8, 1983 which discloses bayonet joint backset adjustment for latch construction. Latch assemblies with backset adjustment which prevent deadbolt axial movement during backset adjustment have been disclosed in U.S. Pat. No. 4,979,768 to Marotto et al. issued on Dec. 25, 1990 and U.S. Pat. No. 5,152,558 to Smith et al. issued on Oct. 6, 1992, yet the constructions of the latch assemblies are too complicated. The present invention is intended to provide an improved design in this regard.